1. Field of the Invention
The present invention relates to an optical communication system, in particular to a broadband high output current output stage applied in a low-cost manufacturing process to achieve the effect of improving the communication capacity.
2. Description of the Related Art
At present, optical communication technology is the mainstream of the high-speed communication network and a middle-distance signal transmission of the optical communication technology generally adopts a direct modulation distributed feedback (DFB) laser light source, and a long-distance signal transmission adopts an external modulation laser (EML) light source. As to the transmission rate, present system manufacturers adopt a mature network technology, namely a coarse wavelength division multiplexing (CWDM) technology having a primary technical specification of OC48 (2.488 Gb/s)˜OC192 (9.953 Gb/s), and gradually advancing to OC768 (39.812 Gb/s).
With reference to FIG. 1 for a high output current output stage produced by a CMOS process, the output stage comprises a first differential pair 1, a second differential pair 2 and a bias unit 3, wherein the first differential pair 1 is connected to a load 4 and the second differential pair 2 respectively, and the second differential pair 2 is connected to a previous driver (pre-driver) for a high current output, and the bias unit 3 is connected to the first differential pair 1. The output stage still cannot meet the bandwidth requirement of 40 Gb/s. In another high output current output stage produced by an indium phosphide (InP) and gallium arsenide (GaAs) process, the bandwidth requirement of 40 Gb/s can be met, but the cost is high, and the mass production is difficult.